The present invention relates to an image forming apparatus for subjecting an input image signal to, for example, a color conversion process, an enlargement/reduction process, etc. in an image forming apparatus, such as a digital copying machine, which reads a color image on an original and produces a copy image thereof.
In general, in a digital copying machine or a laser printer, in order to produce an output image which is clearer and favorably accepted by users, an original to be input or an input image signal is discriminated into a character portion and other portions in units of a pixel or an area by using a discrimination signal, and an image processing method to be carried out within the digital copying machine or laser printer is switched according to the discrimination signal.
Where an input image is to be enlarged or reduced to produce an output image at the request of the user, the discrimination signal, too, may be enlarged/reduced in addition to the enlargement/reduction of the input image, depending on the scheme of the image processing. In the prior art, a fixed discrimination signal has been enlarged/reduced by arithmetic operations, irrespective of characteristics of the input image.
However, there is a case where a proper image process varies depending on whether the input image is an image with emphasis on a gray scale, such as a photographic image, or a character image, or a color image, or a black-and-white image. If the discrimination signal is merely enlarged/reduced without considering this matter, the obtained discrimination signal may designate an image process which is not suitable for the characteristic of the image on the original.